Dyeing cellulose esters



Patented, F eb. 10, 1925.

UNITED STATES PATENT OFFICE.

FRITZ ettnmnnn,

THE BADISCHE QF LUDWIGSHAFEN-ON-THE-RHINE, GERMANY, ASSIGNOR TO ANILIN- & SODA-FABRIK, OF LUDWIGSHAFEN-ON-THE-RHINE,

GERMANY, A COBCPO'RATION OF GERMANY.

In Drawing.

To all whom it may concern."

Be it known that I, FRITZ GtiN'rmsR, citizen of the German Empire, residing at Ludwigshafenbirths-Rhine, Germany, have l invented new and useful Improvements in Dyeing Cellulose Esters, of which the following is a specification.

This invention relates to a process for dyeing cellulose esters which, as is known, has hitherto encountered great difliculty substantially caused by the property possessed by cellulose acetate of having no atfinity for direct or acid coloringmatters.

According to the present invention the dyeing of cellulose esters can besatisfactorily effected by employing insoluble or difiicultly soluble azo dyestuffs in the form of their water soluble bisulfite derivatives. With such derivatives the cellulose acetate 80 can be dyed in-various ways for example from an a weakly acid condition.

bisulfite compound of the azo coloring matter aniline-azo-beta-naphthol has been ascribed the following formulaz' aqueous dyebath at a moderate or hottemperature and the dyeba'th may have For example the Application filed April 9, 1923. Serial No. 630,942.

In orderto illustrate the nature of this invention, the following example is given, 0 but the invention is not restricted'to this example.

The dyebath may contain the bisulfite compound of' the azo coloring matter aniline-azo-beta-naphthol and also a small addition of acetic acid in order to increase its stability which dyebath may be kept at from about degrees to degrees centigrade.

. The cellulose acetate is introduced in a well wetted condition into said dyebath where- 50 upon the temperature of the bath is gradually raised to about 70 degrees to 75 degrees centigrade'. The dyed material is rinsed I with water and then shows a beautiful golden orange color. 7 Bisulfite compounds of other insoluble or difficultly soluble azo dyestufi's and other cellulose esters may be employed in an analogous way.

I claim: 60

1. The process of dyeing cellulose esters, characterized by employing bisulfite compounds of diflicultly soluble or insoluble azo coloring matters.

2. The process of dyeing cellulose acetate silk which consists in treating the silk in a dyebath containing a Water soluble bisulfite compound of a difficultly soluble or insoluble azo coloring matter and in a weak acid condition.

In testimony whereof I have hereunto set In hand.

y FRITZ GUNTHER. Witnesses W. W. Sonorr, V O. (l. L. B. Wms. 

